This invention relates to a self-lubricating bearing.
Self-lubricating bearings are known in the art, and are usually manufactured of such materials as polyamides, polyacetals, polybutylenephthalates, polycarbonates and polytetrafluoroethylene. Although such known bearings have good self-lubricating properties and hence good frictionless properties, they have the distinct disadvantage of being usable only with small loads. They are generally incapable of being operated with large loads. Also the life of such prior bearings is not very long.
To improve such bearings, in the prior art, experiments have been conducted admixing lubricating oil into the synthetic resin. In one case, active carbon was used as a carrier for the oil in the admixing process. Also, other synthetic resins, which can act as a carrier for lubricating oil, have been used. For example, there have been used a copolymer of ethylene-propylene-diene monomers, butadiene rubber, isoprene rubber, etc. However, disadvantageously, the oil carrier comprised of the synthetic rubber do not have a large capacity for absorbing lubricating oil. For example, at most, one volume of rubber will absorb three volumes of lubricating oil. Moreover, when a capacity amount of oil is absorbed, a large amount of synthetic resin is used and thus causes the properties of the main bearing material, such as synthetic resin, to be adversely affected, such as causing a decrease in mechanical strength and decrease in slidability.
It has been found that the known lubricating oil carriers, such as activated carbon, synthetic rubber and metal salts have by themselves very little lubricity. Thus, upon contact of the bearing comprised of such material as carrier, with a corresponding part, such as a rotating shaft, there is no satisfactory slidability. Also, since the above mentioned oil immersed resin, which is the main bearing material, is not subjected to any quality improving treatment of effect high thermal conductivity, low linear expansion, the bearng is liable to be directly and adversely affected by the rotational friction on the contact surface. Both materials would lose their dimensional stability and display the so-called "shaft embracing" and "melt adhesion" phenomena.
Accordingly, there is urgent need existing for a self-lubricating bearing which has good self-lubricating properties and can withstand heavy loads and be utilizable for an extended period of time, and have a long life time.